In the field of speed sensing, a sinusoidal signal may be generated by a magnetic sensor in response to a rotation of a target object, such as a wheel, camshaft, crankshaft, or the like. The sinusoidal signal may be translated into pulses, which is further translated into a movement detection or a speed output.
For example, in speed sensor applications, a speed signal path and a direction signal path may be used. Typically, the speed signal path measures the differential magnetic field on a left positioned sensing element and right positioned sensing element location. The direction path measures the magnetic field with a monocell sensor element placed at a center sensing location. With such a concept, a phase difference or phase shift between the speed signal and direction signal can be evaluated and the rotation direction can be determined from the phase shift. The use of moncells for direction detection has drawbacks in external field robustness and is more affected by electronic noise. Both aspects are getting more important for the implementation of sensors in hybrid and fully electric cars.
In some implementations, the same concept may be used for speed and direction. Two sensor Wheatstone bridges may be used, one for generating the speed signal and one for generating the direction signal, having a displacement between each other. However, a disadvantage with this configuration is that a phase shift between the signals equals the displacement of the two bridges. With a target wheel having a 20 mm pitch and a displacement of the bridges at 1 mm, the resulting phase shift is small (360°/20=18°). Even if the signal amplitude of the direction signal is large, the phase shift is too small to allow a good and robust direction detection.
Therefore, an improved device having better and more robust direction detection may be desirable.